Ionization-measuring instrument



April 10, 1956 FUTTERKNECHT 2,741,706

IONIZATION-MEASURING INSTRUMENT 2 Sheets-Sheet 1 Filed. July 26, 1954INVENTOR: RUDOLF FUTTERKNECHT AGENT April 1956 R. FUTTERKNECHT 2,741,705

IONIZATION-MEASURING INSTRUMENT 2 Sheets-Sheet 2 Filed July 26, 1954INVEN TOR: RUDOLF FUTTERKNECHT AGENT States Patent r 2,741,705 EggPatented Apr. 10, 1956 HEN iZATION -MEASURIN G INSTRUIVIENT RudolfFutterlrnecht, Stuttgart, Germany, assignor to Nassau Distributing Co.,Inc., New York, N. Y., a corporation of New York Application July 26,1954, Serial No. 445,796

15 Ciaims. (Cl. 250-8316) My present invention relates to anionization-measuring instrument of the general type disclosed in my U.S. Patent No. 2,646,516, issued July 21, 1953.

Instruments of the type referred to include a sealed charge generatorcomprising a set of dielectric pellets movable within a housing andadapted to produce, by their movement, a charge across a pair ofcondenser plates which can be read by a suitable indicating device, suchas as electrometer. The two condenser plates define an ionizationchamber Whose atmosphere, when ionized by impinging radiation, willcause a gradual dissipation of the charge at a rate determinable bymeans of the indicator.

In my co-pending application Ser. No. 356,278, filed May 20, 1953, Ihave disclosed an improved version of such instrument wherein the chargegenerator is adapted to be locked, preferably by magnetic means, in areading position in which a first condenser, representing a chargingcapacitance associated with the generator, is efitectively disconnectedfrom a second condenser, representing a storage capacitance associatedwith the indicating device. The presence of this charging capacitance,however small, introduces an element of uncertainty in that it afiectsthe magnitude of the charge stored after a finite number of chargingoperations (shakings or inversions).

An important object of my present invention is to provide an improvedinstrument of the general character referred to in which theaforementioned charging capacitance is substantially eliminated byshort-circuiting after each charging step and in which straycapacitances of a similar character are practically eliminated.

Another important object of this invention is to introduce substantialsimplifications in the construction of such instrument.

In accordance with the instant invention 1' provide a charge generatorin the form of a preferably cylindrical housing, of dielectric material,within which the aforementioned pellets are movable by gravity orinertia between two extreme positions and which is provided with meansfor establishing a conductive path between the generator and one or theother condenser plate in one or the other extreme position,respectively. As in the system of my above-identified co-pendingapplication, the generator is preferably provided with magnetic lockingmeans for immobilizing it in a reading position in which the circuit toat least one of the condenser electrodes is permanently broken.

The invention will be more fully described with reference to theaccompanying drawing in which:

Fig. 1 is a view, in axial section, of an ionizationmeasuring instrumentaccording to the invention, shown in partially discharged condition;

Fig. 2 is a view similar to Fig. 1 but showing the instrument in theprocess of charging by shaking or inversion, the same being illustrated,however, in upright position for easier comparison with Fig. 1;

Fig. 3 is a sectional View taken on the line 3-3 of Fig. 1;

Fig. 4 is a cross-sectional view taken on the line 4-4 of Fig. 1;

Fig. 5 is a cross-sectional view taken on the line 55 of Fig. 2; and

Fig. 6 is a cross-sectional view taken on the line 6-6 of Fig. 1.

Throughout the several views of the drawing I have used, so far asapplicable, the same reference numerals as in my co-pending applicationSer. No. 356,278 to designate similar parts.

The instrument shown in the drawing comprises a housing composed of atubular central body 10 of insu lating material, a cap 11 of similar buthighly transparent material, and a base 12 of insulating material. Thebody 10 is internally lined, over substantially its entire length, witha metallic coating 18 constituting one of the plates of a charge-storingcondenser, the other condenser plate being represented by a similarcoating 15 on a dielectric insert 16 which is press-fitted inside body19. A plastic piston 21, comprising an upper disk 21a, a lower disk 21band a connecting tube 21c, is slidably mounted within insert 16 by meansof an axially extending metal rod 121 traversing the tube 210.Dielectric pellets 42, preferably of quartz glass, occupy part of thespace between disks 21a and 21b.

The rod 121 terminates at its bottom in a cylindrical boss 43 having apin 143 projecting laterally therefrom. This boss is rigid with a metalplate 22 having a radially extending lug 122 which plays in a slot 123of insert 16, whereby the unit 121, 43, 22 is held against rotationwithin this insert but is axially slidable over a short distance limitedby the length of slot 123. The upper end of rod 121 is fixed to a shortmetallic thimble 114 within which a metal ball 31 is held for limitedaxial movement. Thimble 114 is slidably received in an aperture 29 of aflanged spacer member 13 inserted between the housing body 10 and theupper end of insert 16; member 13, which consists of dielectricmaterial, is provided at its underside with a metal plate 13a makingcontact with the outer conductive coating 15 of insert 16 and with thesliding thimble 114.

A plurality of insulating rods 113, rising from the spacer member 13,support a central electrode 14 consisting of a conductively coated,molded plate 14:: and a pair of similarly coated, spaced segments 14b,14c integral with and carried by plate 14a. The segments 14b, 14c definea gap 32 for the movement of an indicating member 33 which comprises asegmental body 33a, a pointer 33b and a reinforced hub portion 330.Member 33 is supported by a pin 34 which spans the gap 32 and isjournaled in bearings 35, 36 extending inwardly from the top of housingportion 19, whereby a metallic connection is formed between thisindicator member and the inner conductive coating 13 of the housing. Ametal rod depends from central electrode 14 and terminates just short ofball 31 in the normal position of the instrument (Figs. 1 and 3).

The transparent cap 11 of the instrument housing is formed integral witha pair of parallel, upstanding walls 11a, 11b substantially aligned withelectrode segments 14b, 14c respectively; wall 11b carries a scale 38cooperating with the pointer 33b.

Press-fitted inside housing portion 10 immediately below insert 16 is ametal ring 17 having a horizontal flange portion 117 which makes contactwith lug 122 when the latter is in its bottom position, as shown in Fig.l. reely rotatable within ring 17 is a metallic retaining member 45, ofinverted cup shape, formed with a roughly segmental cutout 34 as bestseen in Fig. 4. A plastic insert 48 within member .is partly molded withrespect to this member.

The base 12 has a depend platelSa to coating'lS.

ing flange 12a provided externally with an annular groove 50; acon-trolknob 51 is molded arounda bar magnet 52 and has a peripheral portionsurrounding the fiange 12a, this portion having imbedded therein atleast one pin '3 projecting into groove "56 'to hold the knob '51 inplace.

The operation of the instrument shown in the drawing is as follows: I

Knob 51 at the bottom of housing base 12 is manually rotatable between areading position (Fig. l) and a Jdiametrically opposite chargingposition (Fig. 2) which may be'marked on the instrument by suitablelegends and/or indexing means (not shown). In the reading position the"magnet 52 holds the magnet '49 and, thereby, the retaining member 4% ina position in which a solid portion of this retaining member overliesthe pin 143 and the assembly 43, 22 123., 114 is substantiallyimmobilized nearithelower end of its short axial travel. in thisposition, and with the instrument held upright, the charging capacitance15, 18 is 'sh'ort-circuited 'over a conductive path extending frommetallic layer 18 to ring 17 and lug 122 of plate 2.2, rod 121, thimble114 and thence via The position of the pointer 35!: on scale 33 isdetermined by the charge on a storage condenser represented by coating18 and member 33 on the one hand and central electrode 14 on the other.

When the knob '51 is rotated by 180 and the instrument inverted orshaken horizontally into a position as illustrated in Fig. 2, pin 143passes through the cut-out 44 and rod 121 is unlocked. Lug 3122 nowdisengages the ring 117 and breaks the connection between plates '15 and18 of the charging condenser; also, ball 30 conductively connectsthimble 114 to rod 2%, thereby establish ing a path from coating tocentral electrode 1d. At the same time the presence of frictionallycharged pellets 42 "near plate'13a attracts electrons toward the coating15 and positively charges the central electrode 14. When the instrumentis new again righted, or shaken in the opposite direction, electrode 14is again insulated from coating 15 and the aforementioned'shortcircuitacross the capacitance 15S, '15 is reestablished, the negativecharge on coating 15 being thereby communicated to coating 18.

'When, by repetition of the above operations, the instrument has beenfully charged, the pointer 33b will register with the 0-point or" thescale 38 and the lmob 51 may now be returned to reading position. Ifradiation is present, ionization will occur in the space between theplates of the aforementioned storage condenser 14, 13, 33 and thiscondenser will gradually discharge; the rate of the pointers return tono-charge position, or the position reached by the pointer at the end ofa predetermined time interval (as read on the suitably calibrated scale33), will give an accurate indication of the radiation intensity.

It will be noted that the capacitance of charging condenser 15, 18 isconsiderably greater than that of the storage condenser at the top ofthe instrument, and that the two condensers are ,eliectively in parallelWhen'the instrument is inverted and'unlocked, whereby discharges due toionization will occur at a much more rapid rate than in normal readingposition. It is, accordingly, possible to correct overcharges or toproduce limited discharges in this manner even where no appreciableradiation is 'present. More rapid discharges are possible by unlockingthe instrument (as in Fig. 2) and shaking it several times in invertedposition, whereby pellets 42 and ball 30 will move out of step (owing todifferences in weight and mobility) and electrons will be returned tothe central electrode 14.

.My invention is, of course, not limited to the specific embodimentdescribed and illustrated but may be realized in numerous modificationsand adaptations without departing from the spirit andscope of theappended claims.

I claim:

'1. [In an ionizationemeasuring instrument, in combination, a pair ofconductive elements insulated from each other, a charge generatorcomprising charge-carrying means displaceable between two positionsrelatively close to and relatively remote from one of said elements, respectively, electrostatic indicator means comprising a first and asecond electrode relatively remote from said charge-carrying means inboth of said positions, first bridge means for conductively connectingsaid one of said elements to said first electrode in said relativelyclose position of said charge-carrying means, thereby inducing a chargeof predetermined polarity in said one of said elements and a charge ofopposite polarity in said first electrode, second bridge means forconductively interconnecting .said elements in said relatively remoteposition of said charge-carrying means, and means conductivelyinterconnecting the other of said elements and said second electrode atleast in said relatively remote position of said charge-carrying means.

2. The combination according to claim 1, further inclu manually operablemeans for selectively blocking the operation of said ,firstbridge means.

3. In an ionization-measuring instrument, in combination, 'a pair ofconductive elements insulated from each other, a charge generatorcomprising charge-carrying means displaceable between two positionsrelatively close to and relatively remote from one of said elements,respectively, electrostatic indicator means comprising a first and asecond electrode relatively remote from said charge-carrying means inboth of said positions, first bridge means on said charge generator forconductively connecting said one of said elements to said firstelectrode in said relatively close position of said charge carryingmeans, thereby inducing .a charge of predetermined polarity in said oneof said elements and a charge of opposite polarity in said "firstelectrode, secondbridge means on said charge generator for conductivelyinterconnecting said elements in said relatively remote position of saidcharge-carrying means, and means conductively interconnecting the othero'flsaid elements and said second electrode at least in saidrelativelyremote position of said charge-carrying means.

4. The combination according to claim'3, wherein said cbarge'generatorcomprises a tubular container of dielectric material, saidcharge-carrying means being held in said containerfor axial displacementrelative thereto, and an elongated member traversing said container inaxial direction and adapted .to move axially With respect thereto, saidfirst and second bridge means being operative connected with saidmember.

.5. The combination according to claim 4, further including lockingmeans .for substantially immobilizing said member in a position ofinoperativeness of said first bridge means.

6..An apparatus for charging a'pair of electrodes, comprising a firstand a second conductive element insulated from each other, a dielectriccontainer of tubular configuration, charge-carrying means within saidcontainer movable between .a first and .a second axial position andadapted to become irictionally charged by such movement, saidcharge-carrying means being relatively close to said first elementinsaid first position and relatively remote therefrom in said secondposition, bridge means coupled with said container for :conductivelyconnecting said first element to one of said electrodes-in said firstaxial position and for conductively interconnecting said elements'insaid second axial position of 'said charge-carrying means, and meansconductively interconnecting 'said second element and the other of saidelectrodes at least in said second position of said charge-carryingmeans.

7. An apparatus according to claim 6, wherein said elements are a pairofcondenser plates.

8. An apparatus according to claim 6, wherein said container is providedwith a member mounted thereon ior limitedrelative axial displacement,:said bridge means being operatively coupled with said member.

9. An apparatus according to claim 8, wherein said member is a rodaxially traversing said container.

10. An ionization-measuring instrument comprising a charge indicatorincluding a pair of electrodes together defining an ionization chamber,a pair of condenser plates remote from said electrodes, meansconductively connecting one of said condenser plates to one of saidelectrodes, a tubular container of dielectric material, a conductiveelement adjacent one end of said container forming electrically a partof the other of said condenser plates, dielectric charge-carrying meansmovable inside said container between two extreme axial positions closeto and remote from said conductive element, respectively, and adapted tobecome frictionally charged by such movement, first bridge means coupledwith said container for conductively interconnecting said element andthe other of said electrodes in said close axial position of saidcharge-carrying means, and second bridge means coupled with saidcontainer for conductively connecting said 1 element to said one of saidcondenser plates in said remote axial position of said charge-carryingmeans.

11. An instrument according to claim 10, further comprising a housingforming an air-tight enclosure around said indicator, said condenserplates and said container, magnetic control means outside of saidhousing and magnetic follower means inside said housing, said followermeans being adapted to inactivate said first bridge means upon movementof said control means from a charging position to a reading position.

12. An instrument according to claim 10, further comprising an elongatedmember traversing said container in axial direction and mounted thereonfor limited relafive axial displacement, said first and second bridgemeans being operatively coupled to said member.

13. An instrument according to claim 12, wherein said first bridge meanscomprises a metallic retainer mounted on an extremity of said member,adjacent said one end of said container, and a metallic connectortelescoped within said retainer and adapted to engage part of said otherof said electrodes only in an extreme position of said connector and ofsaid member.

14. An instrument according to claim 13, wherein said member is ametallic rod, said second bridge means comprising a metallic partextending from the other extremity of said rod.

15. An instrument according to claim 13, further comprising lockingmeans for substantially immobilizing said member in a position in whichsaid connector is held out of engagement with said other of saidelectrodes, a housing forming an air-tight enclosure around saidindicator, said condenser plates and said container, said locking meanscomprising a magnetic control member outside of said housing and amagnetic follower member inside said housing, said housing comprising asubstantially cylindrical, dielectric wall, said one of said condenserplates being constituted by a conductive coating on the inside of saidwall.

References Cited in the file of this patent UNITED STATES PATENTS2,646,516 Futterknecht July 21, 1953 FOREIGN PATENTS 169,918 GreatBritain Oct. 13, 1921

